We are investigating control of insulin sensitivity and glucose utilization in cultured rat adipose tissue. Under standard conditions this model has impaired insulin response for glucose-1-14C and glucose-6-14C utilization. Insulin sensitivity can be partially preserved by: (a) culture in charcoal-treated 4% albumin with 100% O2 gas phase; or (b) culture with 20% human or fetal calf serum in room air. Current investigation with human serum involves exploration of nutritional and disease factors which govern the response of fat cells. We will study the response of rat fat cells to serum from normal, obese or diabetic patients. In each group, the change in serum response after a glucose or protein load will be studied. We will initiate efforts to isolate the factor responsible for altered insulin sensitivity. There is evidence that lipolysis is accelerated in cultured adipose tissue. We will study extracellular and intracellular fatty acids and glycerol after incubation of cultured adipose tissue with epinephrine and/or insulin. Cyclic AMP will be measured in these incubated adipocytes. Intracellular metabolites of glucose bridging the control steps for glycolysis, gluconeogenesis and glycerolgenesis will be measured in an attempt to locate crossover patterns at points of impairment of glucose utilization. The pyridine nucleotides, ATP, and ADP will also be measured to see the changes in energy metabolites in these conditions.